The CSI: Miami actor will portray Bobby, an ex-boyfriend of Betty's sister Hilda (played by Ana Ortiz) who brings both "romance" and "drama" to the series.

He told TV Guide: "He's an old high school boyfriend, and [he comes] back into their lives. A little romance buds, and there's some drama to go along with it."

Rodriguez further hinted that either sister will become the object of his affections, adding: "Maybe a little bit of both. We'll see how it turns out, but it's going to be a lot of fun and it's really funny."

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This autumn, the 34-year-old will also appear in Tyler Perry's I Can Do Bad All By Myself, which co-stars singer Mary J. Blige.

It was reported earlier that Kristen Johnston - who is said to have bested Paula Abdul for a guest spot on Ugly Betty - described her part on the show as "tragic".

The fourth season of Ugly Betty will have a two-hour premiere on Friday, October 9 on ABC.